diff options
Diffstat (limited to 'mysys/ptr_cmp.c')
| -rw-r--r-- | mysys/ptr_cmp.c | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/mysys/ptr_cmp.c b/mysys/ptr_cmp.c new file mode 100644 index 00000000000..65b2c51aafd --- /dev/null +++ b/mysys/ptr_cmp.c @@ -0,0 +1,158 @@ +/* Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB + + This library is free software; you can redistribute it and/or + modify it under the terms of the GNU Library General Public + License as published by the Free Software Foundation; either + version 2 of the License, or (at your option) any later version. + + This library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public + License along with this library; if not, write to the Free + Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, + MA 02111-1307, USA */ + +/* + get_ptr_compare(len) returns a pointer to a optimal byte-compare function + for a array of stringpointer where all strings have size len. + The bytes are compare as unsigned chars. + Because the size is saved in a static variable. + When using threads the program must have called my_init and the thread + my_init_thread() + */ + +#include "mysys_priv.h" + +static int ptr_compare(uint *compare_length, uchar **a, uchar **b); +static int ptr_compare_0(uint *compare_length, uchar **a, uchar **b); +static int ptr_compare_1(uint *compare_length, uchar **a, uchar **b); +static int ptr_compare_2(uint *compare_length, uchar **a, uchar **b); +static int ptr_compare_3(uint *compare_length, uchar **a, uchar **b); + + /* Get a pointer to a optimal byte-compare function for a given size */ + +qsort2_cmp get_ptr_compare (uint size) +{ + if (size < 4) + return (qsort2_cmp) ptr_compare; + switch (size & 3) { + case 0: return (qsort2_cmp) ptr_compare_0; + case 1: return (qsort2_cmp) ptr_compare_1; + case 2: return (qsort2_cmp) ptr_compare_2; + case 3: return (qsort2_cmp) ptr_compare_3; + } + return 0; /* Impossible */ +} + + + /* + Compare to keys to see witch is smaller. + Loop unrolled to make it quick !! + */ + +#define cmp(N) if (first[N] != last[N]) return (int) first[N] - (int) last[N] + +static int ptr_compare(uint *compare_length, uchar **a, uchar **b) +{ + reg3 int length= *compare_length; + reg1 uchar *first,*last; + + first= *a; last= *b; + while (--length) + { + if (*first++ != *last++) + return (int) first[-1] - (int) last[-1]; + } + return (int) first[0] - (int) last[0]; +} + + +static int ptr_compare_0(uint *compare_length,uchar **a, uchar **b) +{ + reg3 int length= *compare_length; + reg1 uchar *first,*last; + + first= *a; last= *b; + loop: + cmp(0); + cmp(1); + cmp(2); + cmp(3); + if ((length-=4)) + { + first+=4; + last+=4; + goto loop; + } + return (0); +} + + +static int ptr_compare_1(uint *compare_length,uchar **a, uchar **b) +{ + reg3 int length= *compare_length-1; + reg1 uchar *first,*last; + + first= *a+1; last= *b+1; + cmp(-1); + loop: + cmp(0); + cmp(1); + cmp(2); + cmp(3); + if ((length-=4)) + { + first+=4; + last+=4; + goto loop; + } + return (0); +} + +static int ptr_compare_2(uint *compare_length,uchar **a, uchar **b) +{ + reg3 int length= *compare_length-2; + reg1 uchar *first,*last; + + first= *a +2 ; last= *b +2; + cmp(-2); + cmp(-1); + loop: + cmp(0); + cmp(1); + cmp(2); + cmp(3); + if ((length-=4)) + { + first+=4; + last+=4; + goto loop; + } + return (0); +} + +static int ptr_compare_3(uint *compare_length,uchar **a, uchar **b) +{ + reg3 int length= *compare_length-3; + reg1 uchar *first,*last; + + first= *a +3 ; last= *b +3; + cmp(-3); + cmp(-2); + cmp(-1); + loop: + cmp(0); + cmp(1); + cmp(2); + cmp(3); + if ((length-=4)) + { + first+=4; + last+=4; + goto loop; + } + return (0); +} |